1. Field of the Invention
The present invention relates to a lens apparatus, and more particularly, to a lens apparatus provided with an autofocus function.
2. Description of the Related Art
In a lens apparatus used in a television camera or the like, autofocus is known which automatically moves a focus lens to a focusing position according to a high frequency component of an image signal obtained from the television camera. Japanese Patent Application Publication No. 1-158881 discloses a focus adjustment method, in which the operator carries out focus adjustment by manual focus, and then focus adjustment with high accuracy difficult to be visually performed is subsidiary carried out by the autofocus.
However, the above focus adjustment method is basically carried out by the manual focus, requires that the operator carries out focus adjustment visually through a viewfinder until focusing to some extent is obtained, and does not reduce burdens of the operator in the focus adjustment.
On the other hand, in the case of the autofocus that the whole focus adjustment is automatically carried out (which is referred to as autofocus mode), the focus adjustment imposes no burden on the operator. However, the autofocus cannot sometimes determine in which of an infinite or close-up direction a focus is deviated which can be empirically easily determined by the operator. In such a case, in a conventional autofocus, for example, the focus lens is moved to a predetermined direction to detect a focusing position in that direction, and if the focusing position is not detected in that direction, the moving direction is reversed after the focus lens reaches an end to detect the focusing position in the reverse direction. Thus, focusing sometimes requires a long time.
For this reason, as a new autofocus mode, it is considered that in which of an infinite or close-up direction a focus is deviated is determined by an operator, that the operator is only required to demand an autofocus start-up direction, and then that focusing can be rapidly carried out without focus adjustment imposing burdens on the operator.
In achieving such an autofocus mode, it is required to allow the operator to properly demand the autofocus start-up direction and allow the demand to be appropriately determined.
Further, in the autofocus mode, it is considered that the autofocus start-up direction is demanded by the operator by operating a focus operation member used in manual focus, permitting rapid focusing without imposing burdens of focus adjustment on the operator. In this case, switching to the autofocus is automatically carried out from a state where the operator operates the focus operation member demanding the autofocus start-up direction, and on which condition the switching to the autofocus is carried out is important in terms of rapid focusing and operability. In the case where an operation force of the focus operation member (operation torque when the focus operation member is a focus ring) is changed in switching to the autofocus, it is necessary to prevent rapid change of the operation force so as not to give the operator uncomfortable feeling.
Further, in such an autofocus mode, it is considered that there are various aspects of processings after focusing is once completed, and that a preferable processing is different depending on the operator""s preference or a situation.
An object of the present invention is to provide a lens apparatus capable of rapid focusing by autofocus.
Another object of the present invention is to provide a lends apparatus capable of appropriately determining a demand of an autofocus start-up direction which is properly provided by an operator in an autofocus mode where the operator demands the autofocus start-up direction.
Still another object of the present invention is to provide a lens apparatus wherein, in automatically switching to autofocus from a state where an operator operates a focus operation member, a preferable switching condition is selected in terms of rapid focusing and operability, eliminating uncomfortable operation feeling of the focus operation member in switching to the autofocus.
Yet another object of the present invention is to provide a lens apparatus which allows an operator to select an aspect of a processing after completion of focusing to thereby achieve improvement of convenience of an autofocus mode in the autofocus mode where an operator demands an autofocus start-up direction.
According to the present invention, when the operator demands a moving direction of a focus lens, the focus lens is started to be moved in that direction and set to the focusing position existing in the direction, so that focusing can be rapidly carried out in the autofocus if the operator appropriately demands the moving direction. Further, the operator needs only to demand the moving direction of the focus lens, thereby reducing burdens in the focus adjustment.
According to the present invention, when a start of an autofocus mode is instructed, an AF standby state of waiting for the operator to demand the moving direction of the focus lens, that is, an autofocus start-up direction by operating a focus operation member used in manual focus is set, so that an operator can demand the autofocus start-up direction with the same feeling as the manual focus. Also, by recognizing the operation of the focus operation member in the AF standby state as the demand of the autofocus start-up direction, the demand can be appropriately determined.
A function of a quick zoom is generally used when a desired subject is to be zoomed and focused with high accuracy, and automatically switching to the autofocus mode in an interlocked manner with the start of the quick zoom can save trouble of the operation for starting the autofocus mode by the operator.
According to the present invention, when automatically switching from the state where the operator operates the focus operation member to the autofocus, condition of the switching is that a focus evaluation value exceeds a predetermined threshold, so that the autofocus can be started at a level of the focus evaluation value where no malfunction of the autofocus occurs, permitting rapid focusing.
Further, the condition of switching to the autofocus is that a moving amount of the focus lens which moves according to the operation of the focus operation member, or an operation amount of the focus operation member changes more than a predetermined amount, so that a dead zone can be provided on the focus operation member, preventing defects such as a start of the autofocus by a slight motion of the focus operation member unintended by the operator to improve operability.
Further, gradually switching a clutch, which switches focus lens driving from manual to electrical operation, from a manual to electrical state can eliminates a defect of rapid change of the operation force of the focus operation member for manually driving the focus lens by switching to the autofocus, and uncomfortable operation feeling of the focus operation member in switching to the autofocus.
According to the present invention, for a processing after completion of focusing in the autofocus mode where the operator demands the autofocus start-up direction, at least two mode can be selected among a mode of returning to the AF standby state of waiting for the operator to demand the AF start-up direction, mode of automatically finishing the autofocus mode, and mode of moving the focus lens according to an image signal from a camera in such a manner that the focus lens is always in a focusing position, which permits selecting a preferable mode depending on the operator""s preference or the situation, and achieving improvement of convenience of the autofocus mode.